What percentage of system overhead will not result in poor performance for user programs?

The percentage of system overhead that does not result in poor performance for user programs can vary significantly depending on the specific system architecture and workload. Generally, a well-optimized system can tolerate around 10-20% overhead without adversely affecting performance. However, if the overhead exceeds this threshold, it may lead to noticeable slowdowns in user programs. Ultimately, the acceptable level of overhead is context-dependent and should be evaluated based on the particular use case and system capabilities.